1. Field of the Invention
The present invention is directed to a rotary shaft seal and more particularly to a shaft seal suitable for high speed operations. The invention is further directed to a rotary seal of the type described wherein the face pressure with which the moving part contacts the stationery seal face may be set with precision. The invention is further directed to a seal assembly characterized in that it may be readily mounted and de-mounted from the drive shaft and wherein the substitute sacrificial moving part may be readily installed without the necessity of returning the seal assembly to the factory.
2. Description of the Prior Art
The use of rotary seals has, by and large, replaced the use of stuffing box seals. In a conventional rotary seal, a rotating member is pressed against a static surface whereby fluids are precluded from passing through the interface between the static and rotating components of the seal.
Rotary seals are capable of accommodating a significant degree of shaft eccentricity, a capability not found in stuffing boxes.
In high-speed applications, it is desirable that the rotary component of the seal engage the static component with a precisely determined force. In order to provide a long working life, since wear is significant in seals of this sort, it is conventional to employ as a rotary component wear-resistant substances such as carbides, sintered carbon, etc. A deficiency of such substances is their susceptibility to chipping or cracking unless handled with extreme care. In view of the fragility of such substances, a significant amount of damage occurs in the course of shipping and handling the fully assembled seal.
Conventional seals of the type described typically comprise a mounting collar adapted to be coupled to the shaft and a seal-face carrier member. The seal-face carrier is shiftable axially relative to the drive collar. Drive fingers extend from the collar to the seal-face carrier to provide a rotary driving connection between the two components. The respective components are biased apart by a plurality of coil springs, the respective ends of which are mounted in aligned apertures in the collar and seal-face carrier.
As will be apparent from the foregoing, when the seal-face is worn to the point that an unacceptably low sealing force is exerted, it is necessary to separate the seal-face from the collar and substitute a new seal carrier member. This substitution involves aligning the ends of each of the springs (often 20 or more) with a pair of the opposed apertures in the seal-face and the mounting collar. The complexity of effecting this re-mounting usually requires the return of the entire assembly to the factory.